BATTY, Charles J. K.; ROBINSON, Derek W. Commutators and generators. Mathematica Scandinavica, Berkeley, CA, United States, v. 62, p. 303–326, 1988. DOI: 10.7146/math.scand.a-12220. Disponível em: https://journals.msp.org/mscand/article/view/1407. Acesso em: 25 jul. 2026.